A spinosaurid from Thailand (Sao Khua Formation, Early Cretaceous) and a reassessment of Camarillasaurus cirugedae from the Early Cretaceous of Spain

ABSTRACT

We report theropod caudal vertebrae found at Phu Wiang Mountain, Thailand. They resemble the Portuguese Baryonyx and pertain to the Spinosauridae based on the presence of striations on the surface of the transverse process of the caudals, well developed double keels and a deep ventral groove on the centra, two laminae, delimiting three fossae below the transverse process, and posterior caudals having curved, rod-like neural spines with small process at the base. This supports the presence of spinosaurids in the Sao Khua Formation of Thailand. Furthermore, the putative basal ceratosaur Camarillasaurus Sánchez- Hernández and Benton, 2014 from Spain is found here to be a spinosaurid based on the resemblance of the type materials to the Thai spinosaurid described in the present work, as well as the phylogenetic analysis and the similarity to other spinosaurids. In Europe, spinosaurids have been reported from England, Portugal, and Spain. The reassessment of Camarillasaurus adds to the number of this group in this region. The presence of more than one spinosaurid taxon in the same region is common and can be found in the Kem Kem Beds of Morocco, the Araripe Basin of Brazil, the Iberian Peninsula, and the Khorat Plateau of Southeast Asia.

KEYWORDS:

• Spinosauridae
• Siamosaurus
• Camarillasaurus
• Early Cretaceous
• Thailand
• Spain

Acknowledgments

The authors would like to thank M. J. Benton (Bristol) and M. Herrero (Museo de Galve) for providing pictures of Camarillasaurus, A. Milner (London) for providing pictures and information of Baryonyx, C. Hendrickx for the picture of the Portuguese Baryonyx, O. Mateus (Lourinhã) for access to the Portuguese Baryonyx materials, R. Allain (Paris) for the information on the caudal vertebrae of Ichthyovenator, P. Sereno (Chicago) for access to materials of Suchomimus and the cast of the Spinosaurus neotype, Y. Azuma and M. Shibata (Fukui) for access to the cast of Ichthyovenator, S. Suteethorn and V. Suteethorn (both PRC MSU) for general discussion on the discovery of the Thai material. A.S. and P.M.S. thank the staff of Sirindhorn Museum, Kalasin, Thailand and the Phu Wiang Fossil Research Center and Dinosaur Museum, Khon Kaen, Thailand for their help and hospitality. The directors of the museums are greatly appreciated for their permission to study the fossils and support for the project. We thank people who took part in the excavation and preparation of the materials in this study. This work was done during the tenure of A.S. on a scholarship to study in Germany from the Ministry of Science and Technology, Thailand and was partly supported by the Department of Mineral Resources, Thailand via the Sirindhorn Museum and the Phu Wiang Fossil Research Center and Dinosaur Museum. Figure 1, Figure 6, Figure 7, and Figure 8 were executed by Wijanee Sendang (Chiang Mai, Thailand) and are deeply appreciated. Special thanks go to editor and reviewers Gareth Dyke, David Hone, Federico Gianechini, and two anonymous reviewers that improved the quality of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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